Sintered refractory element-silver contact and silver-cadmium oxide contact members are widely used for high electric current applications due to good erosion resistance and superior arc-interruption characteristics with low temperature rise, respectively. A new contact material combining both the good erosion resistance of refractory element-silver contacts and the good arc-extinguishing characteristics of cadmium oxide in the silver-cadmium oxide contact has been discussed in the industry. One major problem associated with fabricating such a contact is the preservation of cadmium oxide during sintering in a reducing atmosphere required for sintering refractory metal composites. For example, the consolidation of cadmium oxide particles in tungsten-silver composites under cadmiumoverpressure in a closed system is not feasible due to the dissolution of cadmium oxide in the liquid silver and the subsequent oxidation of tungsten to tungstic oxide.
Although improvement in arc-erosion resistance is less dramatic in elemental cadmium-containing contacts than contacts with cadmium oxide, the presence of elemental cadmium is also known to improve the arc-erosion resistance of silver and copper contacts because of the conversion of cadmium into oxide during arcing. The purpose and objects of this invention are related to methods of making elemental cadmium-containing refractory metal-silver contacts by a liquid phase sintering technique.